This invention relates to an improved system for reclaiming or separating the oil from a refrigerant in a screw compressor refrigerant system.
In one system recently developed by the Assignee of the present invention, a heated refrigerant from the compressor passes through a reclaim flow vaporizer to separate oil and refrigerant drained from the evaporator. The separated oil is returned to an oil sump, and utilized to again lubricate the components of the compressor. This provides higher viscosity oil.
The basic structure of the reclaimed flow vaporizer taps a discharge refrigerant from a location within, or slightly downstream, the screw compressor that is likely to be quite hot. This discharge refrigerant passes through the reclaim flow vaporizer. A liquid refrigerant/oil mixture from the evaporator is also sent through the reclaim flow vaporizer, but separated from the discharge refrigerant tap. The hot discharge refrigerant boils off the refrigerant in this liquid mixture from the evaporator cooler. The remaining oil is returned to an oil sump.
While the above-referenced system has benefits, under certain operational conditions the tapped refrigerant from a location within or outside the screw compressor side chamber may not be sufficiently hot to efficiently perform the boiling off function. In particular, at different loads, the temperature of this discharge gas is low and hence not as effective as would be desirable.
In a disclosed embodiment of this invention, alternative valves are placed into the system to control the flow of the compressed refrigerant back to the reclaimed flow vaporizer. One alternative line leads from the last pocket of the screw compressor, as was the case in the above-referenced system. The valve is placed on this line and is operable through a control. A second tap leads from the main discharge line and also passes through a selectively open valve also controlled by the control. The control determines which of the two valves should be opened to provide the optimum highest temperature refrigerant to the reclaimed full vaporizer. In a situation where the compressor is operating at the proper amount of compression at full load, or where there is over compression, the maximum temperature will occur in a chamber associated with the last xe2x80x9clobexe2x80x9d of the screw compressor. Thus, under those situations the control will preferably open the valve tapping the discharge refrigerant from that chamber.
However, when there is under compression the valve controlling the line from the chamber is closed and the valve directly from the discharge line is opened. The refrigerant from the discharge line will typically have a higher temperature under this condition. Typically, the control will lower the load on the compressor in this under-compression situation (that is, the compressor will be driven at a slower speed). Eventually, the pressure from the compressor will reach the design pressure for this lower load situation. At that time, the valve from the last compression chamber will again be opened, and the valve from the discharge line will again be closed.
The present invention thus ensures that an optimum temperature refrigerant is utilized to reclaim oil from a liquid refrigerant/oil mixture.